ESTRO 2024 - Abstract Book

S68

Invited Speaker

ESTRO 2024

3433

MRI-guided radiotherapy for head and neck cancer

Panagiotis Balermpas

Zurich University Hospital, Radiation Oncology, Zurich, Switzerland

Abstract:

Magnetic resonance imaging (MRI) is widely used as part of the diagnostic workup and annotation of tumor and organs at risk in head and neck cancer and already considered standard-of-care in most guidelines. This usage was often reported as "MR-guidance" in the past. Nevertheless, the utilization of this imaging modality for further purposes within a radio-oncological treatment remains at its infancy. Currently, the term MR-guidance has a broad meaning, such as using MRI for adaptive treatments, intrafractional MR-gating and tracking, magnetic resonance imaging-based biomarkers to guide treatment (de-)escalation, up to omission of planning-CT and completely MR-only workflows. Within the last decade, first results on MR-guided treatment of head and neck malignancies on the first commercially available dedicated hybrid-platforms, so called MR-linacs, have been reported and further studies are ongoing. The feasibility of this novel technical approach has been already demonstrated, but evidence on potential clinical benefits is still pending. Moreover, implementing MR-imaging features as biomarkers, with even the potential to use these for "biological adaptation" was an already somewhat older idea, as this does not require online imaging and can be performed on seperate diagnostic machines at distinct time-points before, during and after treatment. As an example, evaluation of a possible early treatment response with means of functional MRI-sequences could allow for tailored treatment and possible (de-)escalation strategies. Furthermore, such imaging can allow for better understanding and longitudinal evaluation of organs-at-risk-alterations scuch as the salivary glands and constrictor muscles. Features of diffusion weighted series are currently the most commonly reported for these purposes, but there is already a variety of different MR-based biomarkers, with MR-radiomics being recently in the focus of research. All of these methods and applications are not yet parts of the clinical routine and more research is needed, espcially when compared to other indications. Finally, the lack of valid and consistent reporting of MR-guided radiotherapy is one important hurdle in conducting and comparing clinical trials and implementation of the results in clinicial practice. Purposes of of this teaching lecture are the presentation of all different facets and utilization strategies of MR-guided radiotherapy for head and neck cancer, including current evidence, data and challenges and the clarification of factors and characteristics important for reporting.

3434

MR-Linac: A new workflow

Nienke Weitkamp, Anne M.E. Bruynzeel, Miguel A Palacios